A power seat in which a lifter adjustment mechanism, a tilt adjustment mechanism, a slide adjustment mechanism and a reclining angle adjustment mechanism are operated by a single motor is disclosed in JP-A-2013-107624. Power of the motor is transmitted to each mechanism via a power transmission cable. The motor, the lifter adjustment mechanism and the tilt adjustment mechanism are fixed to a side frame that is a framework member of the seat. On the other hand, the slide adjustment mechanism is fixed to a slide rail.
When the lifter adjustment mechanism is operated, a height of the side frame with respect to the slide rail is changed. Therefore, a relative distance between the motor fixed to the side frame and the slide adjustment mechanism fixed to the slide rail is changed by the operation of the lifter adjustment mechanism. A change in the relative distance is absorbed by a change in the degree of curvature of the power transmission cable arranged between the motor and the slide adjustment mechanism.
FIG. 8 shows the change in the degree of curvature of the power transmission cable. A height of a cable connector 151 connected to a side frame side is changed in response to a change in height of the side frame due to the lifter adjustment mechanism. On the other hand, a height of a sliding gear box 113 of the slide adjustment mechanism is invariable. As a result, the degree of curvature of a power transmission cable 116 disposed between the cable connector 151 and the sliding gear box 113 is changed. The degree of curvature of the power transmission cable 116 is increased as the height of the side frame is lowered from a state where the side frame is set at the highest position. The reason is that the relative distance between the cable connector 151 and the sliding gear box 113 becomes longest in the state where the side frame is set at the highest position and the relative distance between the cable connector 151 and the sliding gear box 113 becomes shortest in the state where a side frame is set at the lowest position. Compared to a power transmission cable 116 (UM) in the state where the side frame is set at the highest position, the degree of curvature is increased as the height of the side frame is lowered as indicated by a power transmission cable 116 (N) and a power transmission cable 116 (DM).
A change in the degree of curvature of the power transmission cable changes efficiency of the power transmission. Therefore, an operation speed of the slide adjustment mechanism is changed depending on the degree of curvature of the power transmission cable. Further, in a state where the degree of curvature of the power transmission cable is increased, operation noise of the power transmission cable is increased. Therefore, in a state where the relative distance between the motor and the slide adjustment mechanism is reduced and the degree of curvature of the power transmission cable is increased, noise of an operation of the slide adjustment mechanism is increased.